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Old 07-25-2020, 07:32 PM   #151
popgun pete
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Re: The Infinite Engines Dreamair moves from dream to reality

New single barrel alloy gun in a carbon fiber hull.
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Old 07-25-2020, 10:01 PM   #152
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Re: The Infinite Engines Dreamair moves from dream to reality

I was wondering the same thing. Could it be because the compression ratio is so much higher to the point where the CVT can’t invert the loading force?


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Old 07-26-2020, 12:44 AM   #153
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Re: The Infinite Engines Dreamair moves from dream to reality

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Originally Posted by Diving Gecko View Post
I was wondering the same thing. Could it be because the compression ratio is so much higher to the point where the CVT can’t invert the loading force?


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Looking back at the original oval cross-section tank alloy gun it had a compression ratio of about 2.0, so I don't think there is a problem there. If you take an outer winding drum and measure the length of its spiral track then that has to bridge the distance from the drum top (or bottom) to the rearmost shaft tab. As you cannot stretch the cable it needs to make it! The inner winding drum has a spiral track length that determines the stroke of the piston in the barrel tube, so this length needs to be smaller than the wishbone draw which creates a narrow triangle with each side of the cable being the required length. Using a monotube for tank and barrel you can use about half of it for the piston travel which gives a compression ratio of 2.0. More than 2.0 has rarely been used in a pneumatic gun unless it had a hydropump.

When you have two extra side chambers you can use a much longer piston travel in the central tube and still keep the compression ratio not too high and we now know that it is around 1.5. That means the inner drum must have a longer spiral track and will be larger in its range of diameters as the width of the winding drums is the same if the guns all use the same size piston. With the oval tank gun the inner drum may have been wider which affects how much track you can incorporate onto it.

The larger the range of diameters on the individual drums then the more variation you can have in the gearing and if you have a longer piston stroke then the diameter change needs to be greater on the inner drum being used to create the longer stroke. For example if you wind a cable on a tapered rod then you will not get as much length as if you wind it on a wooden spinning top because the surface area of the top is much greater and the range of diameters is greater over its surface. This is just my guess, but the longer the piston travel then you have more options with the gearing in terms of the maximum ratio of the drum radii going from outer to inner and vice versa.

Bear in mind that the winding drums photos are from that oval tank gun, they may now be different in their tapered profile and sizes.
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Old 07-26-2020, 05:28 PM   #154
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Re: The Infinite Engines Dreamair moves from dream to reality

Another view of the gun and the hand pump for pressurizing it at the start of the season.
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Old 07-26-2020, 10:05 PM   #155
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The Infinite Engines Dreamair moves from dream to reality

Just a thought but the “inverted loading” could also me missing if Andreas wanted to save that feature for the other more expensive guns. So, a way of differentiating the guns more.
Let’s say the reason for the different loading force diagram is down to using a non-tapered drum on the inside. I wouldn’t think the cost savings of that change would be much in terms of manufacturing. But a lot of companies go to great lengths to protect their high end product by removing features at the lower end that actually don’t cost that much to put in.
(As often is the case with my posts on the subject of this gun, it’s purely speculation).


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Old 07-27-2020, 12:38 AM   #156
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Re: The Infinite Engines Dreamair moves from dream to reality

I am more curious about how the carbon fiber gun goes together, especially inserting and removing the piston. In the original gun the layout was much like a standard pneumatic, you had a muzzle which carries the winding drums, a length of barrel extrusion and a rear handle and shock absorber unit that bolted on the rear of the tank which was the barrel. I don’t see any joins in the “Carbon Unreal” gun, although there must be some to allow it to be assembled and to allow periodic changing of the inner cable. The axle and drums can be removed as before by the threaded bearing mounts, but accessing the “inner works” is now not so obvious.

The attachment shows the original assembly. The other shows how the gun was serviced with its special spanner.
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Old 07-27-2020, 01:29 AM   #157
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Re: The Infinite Engines Dreamair moves from dream to reality

Inner cable sweeps the interior as the inner drum winds in the piston, as shown in the sketch. The bore size of the barrel determines whether it has a free path without touching anything as it traverses the surface of the drum. The gun will be longer than the sketch image shows, but gives a general idea of how it needs to work.
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Old 08-01-2020, 05:29 PM   #158
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Re: The Infinite Engines Dreamair moves from dream to reality

Another video. In this video we see the gun floating after the shot, tail down due to the reel. All carbon version of the "Dreamair".
https://youtu.be/bSAp5SMwers

Moment of hit.
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Old 08-01-2020, 05:49 PM   #159
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Re: The Infinite Engines Dreamair moves from dream to reality

In this next video the alloy internal barrel gun is shown in action, note the changing graph displayed on the left hand side of the screen as shots are taken at different ranges
https://youtu.be/E9-hmkNtW6Y
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Old 08-02-2020, 02:56 AM   #160
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Re: The Infinite Engines Dreamair moves from dream to reality

Quote:
Originally Posted by Diving Gecko View Post
Just a thought but the “inverted loading” could also me missing if Andreas wanted to save that feature for the other more expensive guns. So, a way of differentiating the guns more.
Let’s say the reason for the different loading force diagram is down to using a non-tapered drum on the inside. I wouldn’t think the cost savings of that change would be much in terms of manufacturing. But a lot of companies go to great lengths to protect their high end product by removing features at the lower end that actually don’t cost that much to put in.
(As often is the case with my posts on the subject of this gun, it’s purely speculation).


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Looks like you are right, the inner drum is more of a cylinder, so its contribution to gearing is fixed in the single alloy barrel model. You would still have some gearing in the beehive shaped outer drums, but the advantage is less than with spiral track drums on both. One needs to remember that the shot is the loading effort replayed in reverse, hence provided you can cock the gun it does not really matter. On a standard pneumatic the compression ratio is about 1.10, so the force at latch is 10% greater. Might not sound much, but with pneumatic guns that are pumped right up that extra 10% can be an eye-popping effort with your arm in a position where you cannot apply much more grunt. If the gun had a constant pressure then loading would be easier, but that would require a massive air reservoir allowing the gun to have a compression ratio of 1.0. Now with the Dreamair you can offset that 10%, or part of it, by the gearing system offered by the spiral drums. That means you have a chance of loading it at higher pressures, so any gearing helps. In fact you really need it as the compression ratio is about 1.50, that is 50% more effort at latch.

The downside, if say you are comparing it to a two band gun, is that in effect you load both bands at once, there is no splitting of the loading effort. That is why for higher pressure you need the Dreamloader, which stages your effort rather than splits it. Compressed air is a lot more efficient at energy storage than rubber bands, but losses in the drum and sliding piston system are unknown, although they should be low with some energy being required to spin the drums and axle.
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